Typically, conductive nanocarbon, such as carbon nanotubes (CNT), graphene, and carbon fiber, is applicable in a variety of fields, including electrode materials for transparent electrodes, antistatic devices, electromagnetic wave-shielding devices and energy generation/storage devices, heat-dissipating materials, polymer composites, metal composites, ceramic composites, and conductive fibers. In order to coat nanocarbon or manufacture a nanocarbon fiber, a coating solution or spinning dope in the form of a high-viscosity paste or a diluted solution is required.
To prepare a coating solution or paste, a dispersant such as a surfactant, a copolymer, or an ionic liquid is essentially used. In the case where an excess amount of a functional group is introduced to the surface of a material, the dispersal process is easy but conductivity may decrease. Thus, in the case where a conductive coating solution or paste is prepared using conductive nanocarbon while maintaining conductivity without the use of a dispersant, the manufacturing cost may be decreased, and moreover, the manufacturing process may be simplified. Furthermore, combination thereof with any kind of binder, metal and metal oxide is possible because the dispersant is obviated.
There have been reported techniques for introducing metal particles to increase the electrical conductivity of nanocarbon. With regard to conventional techniques for hybridizing nanocarbon with a nanometal, Korean Patent No. 10-1410854 discloses a highly conductive material formed by hybridizing a nanometal with a nanocarbon material having a higher-order structure due to the presence of multiple hydrogen bonds, and a method of manufacturing the same. In this technique, conductive nanocarbon is introduced with a functional group that enables the formation of multiple hydrogen bonds, thus forming a nanocarbon material having a higher-order structure via multiple hydrogen bonds therein, and the nanocarbon material having the higher-order structure is simply mixed with a nanometal, resulting in a hybrid material. This conventional technique exhibits high dispersibility but is problematic because the nanocarbon and the nanometal are individually distributed due to the bonding properties thereof and thus superior metal properties are difficult to manifest.
In addition, Korean Patent No. 10-0961914 discloses a method of manufacturing a carbon nanotube nanocomposite coated with silver nanoparticles. This method includes a first step of preparing a carbon nanotube dispersion by dispersing carbon nanotubes in an organic solvent, a second step of attaching silver nanoparticles to the surface of the carbon nanotubes by mixing the carbon nanotube dispersion with a solution including silver ions, and a third step of subjecting the product of the second step to centrifugation and washing. In this technique, silver ions are reduced into silver particles in the presence of carbon nanotubes to form a composite of silver nanoparticles and carbon nanotubes, but the silver particles are configured such that spherical nanoparticles are not continuously formed, making it difficult to apply such a composite to highly conductive electrodes. Moreover, since the functional group of the carbon nanotubes has silver particles introduced thereto, the dispersibility of the composite is remarkably decreased in the solvent after the introduction of silver particles, and thus, an additional dispersant has to be used, which is undesirable.